In-Situ Studies of the Electrodeposition of Polymer Networks as Conformal Ultrathin Coatings

Most natural<b> </b>systems, synthetic materials, and devices feature thin films and interphases that control the flow of mass and energy or stabilize incompatible materials. Thin-film coatings on planar and macroscale structures are enabling and performance-determining in technologies such as electronics, structural composites, touch screens, and even simple commodities such as sunglasses. Polymer networks are of particular interest for their tunable chemical and physical properties combined with their structural integrity. With technologies transitioning to non-planar and three-dimensional architectures, novel deposition methods for realizing conformal thin films are required. To this end, we introduce the Electrodeposition of Polymer Networks (EPoN) as a general approach to uniformly coat polymeric thin films on planar and non-planar conductive materials alike. Conceptually, EPoN utilizes electrochemical crosslinkers as a minority component as low as 1% of the polymer to confine the network formation exclusively to the surface upon charge transfer, yielding a passivating and self-limiting growth of conformal and uniform thin films with tunable 10-500 nm in thickness. Generally, the modular polymer design allows for the decoupling of the thin film functionality from its deposition chemistry, though we find that the thin film properties are also dependent on the deposition protocol and conditions. To understand these composition-processing-property relationships of our novel EPoN concept and the derived thin films, we investigate their growth in situ, including deposition in Electrochemical Quartz-Crystal Microbalance with Dissipation (E-QCM-D). In these studies, we find a substantial influence of the deposition potential on the thin film growth stages, including the solvent-film interactions during growth, for example, which alter the resulting thin film properties such as thickness and permeability. The knowledge gained from our in-situ growth studies enables further tunability of the thin film properties, and also broadens the applicability of EPoN to various polymer architectures and electrochemical crosslinkers by providing general design criteria.